In a final stage of oil refining process, heavy oil is produced which is generally divided into three different classes, i.e., heavy oil type A, heavy oil type B and heavy oil type C in accordance with their viscosity. Since heavy oil generates high calory (more than 10,000 Kcal/Kg) and is relatively inexpensive and easy to handle, it is estimated that the commercial consumption of heavy oil accounts for nearly 70%-80% of all oil products which are used in Japan for facilities in various industries including large scale heating facilities and large vessels.
When heavy oil, in particular high viscosity heavy oil such as heavy oil B and heavy oil C, is burnt, a large volume of pollutants, such as, sulphur oxide, nitrogen oxide, carbon monoxide, soot and dust is generated. If no effective antipollution countermeasure is taken, these pollutants can contaminate the environment and pose a serious threat to the ecological system. Accordingly, the Japanese government sets various standards regarding the maximum permissible discharge levels of toxic pollutants for facilities which burn heavy oil. The government imposes on the industries strict preventive measures to keep the discharge level below the standard level. As a result, the industries in which heavy oil is used as a fuel generally tend to make substantially large investments to equip heavy oil burning facilities with highly complex and expensive antipollution devices and facilities.
However, these antipollution devices and facilities tend to become more complex and expensive, particularly when lower grade oil, such as heavy oil C, is used. Major electric companies, for example, use heavy oil C because heavy oil C is relatively inexpensive as compared with heavy oil A and B, although heavy oil C generates more pollutants. In order to comply with the government antipollution standard and regulation, these electric companies have to make substantial investments in antipollution facilities or, alternatively, mix heavy oil C with heavy oil A or heavy oil B in order to reduce emission of pollutants, resulting in a substantial increase in cost. Furthermore, a perfect combustion of heavy oil B and heavy oil C is relatively difficult unless they are sprayed into substantially small particles.
It is appreciated that, when heavy oil is used for the operation of, for example a boiler, heavy oil is sprayed by a jet injector to form a jet stream of very fine particles in order to achieve a satisfactory combustion. However, the jet stream itself tends to disrupt the combustion of the particles of heavy oil. This will lower the thermal efficiency of the boiler. In order to improve the thermal efficiency, the air/oil ratio may be adjusted. However, such an adjustment of air/oil ratio tends to enlarge the size of oil particles, and results in imperfect combustion of heavy oil and thus higher emission of pollutants.
Waste oil may be burnt for treatment. In facilities where waste oil is generated as a result of routine operations, such as, waste machine oil at a garage or a factory, waste machine oil may be separated into a reusable part, a non-reusable part, water, etc. In accordance with the Japanese government antipollution regulations, the non-reusable oil must be completely burnt in an incinerator while controlling the emission of pollutants below the strict discharge levels set by the government.
Water may be separated by using a waste oil purification separator tank or by natural separation of water from oil during storage. While the separated water generally does not appear to contain any waste oil, the water has offensive smell because it is contaminated with the waste oil. Therefore, the separated water must be thoroughly filtered and purified to completely remove oil content therefrom before the water is discharged. If this separated water is discharged into a river or a lake without a proper filtration or a purification treatment, the river or the lake will be contaminated. To filter and purify the separated water, a water filtration and purification facility is required, in addition to the waste oil treatment facilities.